RU2401881C2 - Coating method and device, permanent magnet and method of making said magnet - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: permanent magnet is made by applying a Dy coating onto the surface of a Fe-B-rare-earth element magnet having a predetermined configuration and diffusion of Dy deposited on the surface of the magnet into boundary phases of crystalline grains of the magnet through thermal treatment at a predefined temperature. The step for applying the coating involves a first stage for heating a working chamber used at the step for applying the coating and creating an atmosphere of metal vapours inside the working chamber by evaporating evaporable metallic material inside the working chamber, and a second step for putting the magnet into the working chamber whereby the said magnet is kept at temperature lower than that of the working chamber, and then selective deposition of the evaporated metallic material onto the surface of the magnet under the effect of temperature difference between the working chamber and the magnet while temperature of the magnet reaches a predefined value. ^ EFFECT: increased efficiency of making a permanent magnet with low cost of the magnet. ^ 21 cl, 12 dwg, 8 ex

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0001] The present invention relates to a coating method and apparatus, a permanent magnet and a manufacturing method thereof, and more particularly, to a permanent magnet and a manufacturing method thereof, in which a permanent magnet is manufactured by depositing an evaporated metal material comprising at least one of Dy and Tb, to the surface of a magnet of the type Fe-B-rare earth elements and subsequent diffusion of at least one of Dy and Tb into the boundary phases of the crystalline grains of the sintered magnet by heat treatment and the metal to be vaporized at a predetermined temperature, as well as to a coating method and apparatus suitable for applying the vaporized metal material containing at least one of Dy and Tb to the surface of the magnet.

Description of the prior art

[0002] Recently, a sintered Nd-Fe-B magnet (a so-called neodymium magnet) has been used in various products, for example, in hybrid vehicle engines and generators, etc., since a neodymium magnet can be made from a combination of Fe, Nd and B, which are cheap, available in sufficient quantities and stably available resources, and also has high magnetic properties (its maximum energy product is 10 times greater than that of a ferrite magnet). On the other hand, the problem is that the sintered Nd-Fe-B magnet is demagnetized by heat when it is heated above a certain temperature, so its Curie temperature is low and is 300 ° C.

[0003] Therefore, in the manufacture of the sintered Nd-Fe-B magnet, since Dy and Tb have a 4f-electron magnetic anisotropy greater than that of Nd and have a negative Stevens factor, like Nd, it can be predicted that the addition Dy or Tb will significantly increase the magnetocrystalline anisotropy of the main phase. However, since Dy and Tb acquire a ferromagnetism structure in which the orientation of the Dy and Tb spins is opposite to that of the Nd spins in the crystal lattice of the main phase, this causes the problem that the magnetic field strength is significantly reduced, and therefore the maximum energy product that determines magnetic properties.

[0004] To solve this problem, it is proposed to first apply Dy and Tb to the entire surface of the sintered Nd-Fe-B magnet having a predetermined configuration, such as a rectangular parallelepiped, with a predetermined coating thickness (thickness greater than 3 μm, determined based on the volume of the magnet ), and then ensure uniform diffusion of Dy and Tb deposited on the surface of the magnet to the boundary phases of the crystalline grains of the magnet during heat treatment at a predetermined temperature (see Non-Patent Document 1, below).

[0005] A permanent magnet manufactured in accordance with this method has the advantages that a coercive force generating mechanism such as core formation is enhanced by the fact that Dy and Tb, diffused into the boundary phases of the crystal grains, increase magnetocrystalline anisotropy in the surface of each crystalline grain, as a result of which the coercive force increases significantly without reducing the maximum energy product (for example, non-patent document 1 askryvaet that can have a magnet having a coercive force of 23 kOe (3 MA / m) at a remanence of 14.5 kG (1.45 Tesla), and the maximum energy product of 50 MGOe (400 kJ / m ^3)). When applying Dy or Tb to the surface of the sintered Nd-Fe-B magnet, it is possible to use a sputtering method that provides excellent adhesion of Dy and Tb to the surface of the sintered magnet.

Note: Non-Patent Document 1: “Improvement of coercivity on thin Nd2Fel4B sintered permanent magnets” (Park Ki Te, Doctoral dissertation defended at the University of Tokyo, March 23, 2000).

Disclosure of invention

Problems Solved by the Invention

[0006] However, since the spraying method has poor efficiency in using the spray target and the output of the evaporated metal material for coating, it is not suitable for coating of Dy or Tb, which are scarce materials, and therefore cannot be expected to be delivered in sufficient quantities. In addition, in order to cover the entire surface of a magnet having a predetermined configuration, such as a rectangular box, using the spraying method, it is necessary to rotate the magnet itself, and therefore, some kind of mechanism is required to rotate the magnet. This further increases the cost of manufacturing a magnet, in addition to the cost of manufacturing a sputtering target from Dy or Tb, which are rare and expensive.

SUMMARY OF THE INVENTION

[0007] Therefore, the first objective of the present invention is to provide a permanent magnet and a method for manufacturing it, which can produce a magnet with low cost by effectively using Dy and Tb as a coating material and applying them to the surface of a Fe-B rare earth magnet having predefined configuration.

[0008] A second objective of the present invention is also to provide a coating method and a coating device that can provide a high yield of evaporated metal material to produce a coating and a substantially uniform coating with high speed over the entire surface of the coated article (ie, sintered magnet) having a predetermined configuration, and which are suitable, in particular, for depositing Dy and Tb on the surface of a magnet of the type Fe-B rare earth elements having a predetermined configuration.

Means of achieving goals

[0009] In order to achieve the objective of the present invention, the present invention provides a coating method comprising a first step of heating the working chamber and creating an atmosphere of metal vapor inside the working chamber by evaporating an evaporated metal material previously placed in the working chamber, and a second introduction step into the working chamber of the coated products, maintained at a lower temperature than the temperature in the working chamber, and subsequent selective deposition of the vaporized etallicheskogo material on the surface coated products under temperature difference between the temperature in the processing chamber and the temperature of objects to be coated.

[0010] Since, in accordance with the coating method of the present invention, a metal coating is formed by selectively depositing the vaporized metal material on the surface of the coated article under the influence of the temperature difference between the temperature in the working chamber and the temperature of the coated articles, it is possible to achieve a high yield of evaporated metallic material upon coating and cover the entire surface of the coated product having a predetermined configuration with high speed.

[0011] In such a case, it is preferable that the atmosphere of the metal vapors is in a saturated state in the working chamber in order to enable coating at a higher rate.

[0012] Also in accordance with the present invention, there is provided a coating device including a working chamber, which can substantially uniformly heat the interior of the working chamber to a high temperature by means of heating means, a preparatory chamber communicating with the working chamber, a vacuum means for maintaining working and preparatory chambers of a predetermined vacuum level, means of opening / closing, moving between an open position in which the working and preparatory to the measures are communicated with each other, and in a closed position in which the working chamber is tightly closed, and a transport means that can move the products to be covered between the working chamber and the preparation chamber and can tightly close the working chamber when the coated product is moved to the working chamber when the means are open opening / closing, while the working chamber heats up when the open / close means is closed, the atmosphere of metal vapor is created by evaporation of the vaporized of the material previously placed inside the working chamber, the coated products in the preparatory chamber are moved to the working chamber by means of a transport means when the opening / closing means is moved to the open position to selectively deposit the evaporated metal material on the surface of the coated product under the influence of the temperature difference between the temperature in the working chamber and temperature of coated products.

[0013] In this coating device, both the working chamber and the preparation chamber are evacuated to a predetermined vacuum level by means of a vacuum means after the coated products have been placed in the preparation chamber. Then, when the working chamber is heated, after the opening / closing means is moved to the closed position by tightly closing the working chamber, an atmosphere of metal vapors is created in the working chamber by evaporation of the vaporized metal material previously placed in the working chamber. Then, the opening / closing means is moved to the open position, and the products to be coated are moved from the preparation chamber to the working chamber by means of a transport means. When coated products, maintained at a temperature lower than the temperature in the working chamber (for example, products with ordinary temperature), are placed in the working chamber, metal atoms in the atmosphere of metal vapor are selectively deposited only on the surface of the coated product with high speed. Thus, it is possible to provide a high yield of evaporated metal material upon receipt of the coating and cover the entire surface of the product having a predetermined configuration with high speed.

[0014] In this case, it is preferable that the working chamber is located inside a vacuum chamber equipped with another evacuating means and is formed by a uniformly heating plate made with an opening in one of its sides, the heat-insulating element is placed so that it encloses uniformly a heating plate, in addition to the specified side of a uniformly heating plate in which said hole is made, and heating means for heating a uniformly heated formation Ini is located between a uniformly heating plate and a heat-insulating element. This design allows the heating chamber to be substantially uniformly heated by heating a uniformly heated plate using heating means and by indirectly heating the working chamber through a uniformly heated plate.

[0015] It is also preferred that the coating device further comprises gas supply means for supplying inert gas to the preparation chamber, and that inert gas is supplied to the preparation chamber via said gas supply means so as to maintain a negative pressure in the working chamber with respect to pressure in the preparatory chamber. This design prevents the vaporized metal material from flowing into the preparation chamber under the influence of the pressure difference between the working chamber and the preparation chamber, when the opening / closing means is moved to the closed position to introduce the articles to be coated into the working chamber after the atmosphere has been created in the working chamber metal vapors.

[0016] On the other hand, it is preferable that the preparation chamber be equipped with gas supply means for supplying helium gas (He) to the preparation chamber, and that helium gas (He) is supplied to the preparation chamber through the gas supply means so as to maintain pressure in the working chamber is essentially the same as in the preparatory chamber. This design prevents the vaporized metal material from flowing into the preparation chamber due to the difference in specific gravity between the working chamber and the preparation chamber, when the opening / closing means is moved to the open position to introduce the articles to be coated into the working chamber after it has been in the working chamber an atmosphere of metallic vapor has been created.

[0017] In this case, it is preferable that the working chamber is located under the preparation chamber.

[0018] It is also preferred that the coating device further comprises placement means on which the vaporized metal material can be placed inside the working chamber, and this placement medium is made in the form of a ring so that the vaporized metal material can be positioned around the articles to be coated when these the products to be coated are moved to the working chamber by means of a transport means. This allows you to evenly heat the evaporated metal material in any part of the placement means and thereby obtain a more uniform coating.

[0019] In addition, it is preferable that the preparatory chamber was equipped with a plasma generating means for cleaning the surface of the coated product using plasma.

[0020] On the other hand, it is also preferable that the preparatory chamber be equipped with other heating means for cleaning the surface of the coated article by heat treatment while supplying an inert gas to a vacuum atmosphere or the preparatory chamber through a gas supply means connected thereto.

[0021] Preferably, the metal material to be evaporated is an alloy containing any of Dy or Tb or containing at least one of Dy and Tb, and the coated article is a sintered magnet of the type Fe-B rare earth having a predetermined configuration.

[0022] In addition, in accordance with the present invention, there is provided a method for manufacturing a permanent magnet, comprising the steps of coating an evaporated metal material containing at least one of Dy and Tb on a surface of a Fe-B rare earth magnet having a predetermined configuration and diffusion of the evaporated metal material deposited on the surface of the magnet into the boundary phases of the crystalline grains of the sintered magnet by heat treatment of the evaporated metal material at a predetermined temperature, characterized in that the coating step includes the first step of heating the working chamber used to perform the coating step and creating an atmosphere of metal vapor in the working chamber by evaporating the vaporized metal material previously placed inside the working chamber, and the second stage of the introduction into the working chamber of a magnet, maintained at a lower temperature than the temperature in the working chamber, and subsequent selective deposition sparyaemogo metallic material on the magnet surface under the influence of the temperature difference between the temperature in the processing chamber and the temperature of the magnet while the magnet reaches a predetermined temperature.

[0023] According to such a manufacturing method, an atmosphere of metal vapor is created by heating the working chamber after the vaporized metal material containing at least one of Dy and Tb used as the coating material has been placed in the working chamber. Then, when coated products maintained at a temperature lower than the temperature in the working chamber (for example, products with a normal temperature) are placed in a working chamber heated to a high temperature, metal atoms, including Dy and Tb, are selectively deposited in the atmosphere of metal vapors only on the surface of the coated product at high speed. Then the evaporation stops after holding the magnet in this state for a predetermined period of time until the magnet reaches a predetermined temperature. Therefore, an evaporated metal material comprising at least one of Dy and Tb can rapidly form a coating of a predetermined thickness on the surface of the magnet, and thus, the production capacity of the magnet can be increased. In addition, since the vaporized metal material containing at least one of Dy and Tb is selectively deposited only on the surface of the coated article, it is possible to efficiently use Dy and Tb, which are rare and have a high cost, and thus reduce the cost of manufacturing a magnet.

[0024] Preferably, the atmosphere of the metal vapors is in a saturated state in the working chamber in order to increase the rate of deposition of the vaporized metal material containing at least one of Dy and Tb on the magnet surface. Although it is possible to use inert gases in the working chamber, in addition to the vapor of evaporated metal materials containing at least one of Dy and Tb, the maximum coating speed can be achieved when the full pressure in the working chamber is created by saturated vapors of evaporated metal materials containing at least one of Dy and Tb.

[0025] The melting temperature of Dy and Tb is high, and therefore, it is preferable that the vaporized metal material additionally contains at least one of Nd, Pr, Al, Cu, Ga and Ta to create an atmosphere of metal vapor in the working chamber for a short time. This makes it possible to additionally increase the coercive force in comparison with a permanent magnet made by heat treatment in the case of, for example, coating only from Dy.

[0026] Incidentally, when a magnet of ordinary temperature is placed in a working chamber heated to a high temperature, the magnet itself is also heated by radiated heat. Then, when this magnet heats up and thermally expands, peeling of the coating deposited on the surface of the magnet can occur, due to the fact that thermal expansion reveals anomalies, as in the Invar alloy at a temperature below the Curie point. Therefore, it is preferable that the predetermined temperature in the second step is below 250 ° C or above 450 ° C. This is because peeling of the coating deposited on the surface of the magnet is difficult because the stress due to thermal expansion anomalies decreases at temperatures below 250 ° C, and, on the other hand, the adhesion between the magnet and at least one of Dy and Tb, deposited on the surface of the magnet is improved by melting part of the magnet, and therefore, at temperatures above 450 ° C, peeling of the coating deposited on the surface of the magnet is difficult.

[0027] In this case, it is preferable that the method of manufacturing a permanent magnet further includes the step of cleaning the surface of the magnet in a vacuum atmosphere before introducing into the working chamber a magnet maintained at a lower temperature than the temperature in the working chamber. This allows, for example, to remove the oxide film on the surface of the magnet and, thus, increase the adhesion force of the vaporized metal material containing one of Dy and Tb to the surface of the magnet, and also makes it possible to uniformly diffuse Dy and Tb deposited on the surface of the magnet into the boundary phase of the crystal grains of the magnet during the diffusion phase.

[0028] It is also preferable that the temperature in the working chamber in the first step be set in the range of 1000-1700 ° C. This is explained by the fact that at temperatures below 1000 ° C, vapor pressure cannot be obtained, which can ensure the deposition of an evaporated metal material containing at least one of Dy and Tb at a high speed on the surface of the magnet, and, on the other hand, at temperatures above 1700 ° C, the magnet coating period becomes too short to obtain a uniform coating.

[0029] It is also preferable that the particle diameter of the vaporized metal material placed inside the working chamber in the coating step be in the range of 10-1000 μm. This is explained by the fact that, when the particle diameter is less than 10 μm, the handling of Dy and Tb particles, which are easily ignited, is difficult, and, on the other hand, when the particle diameter is more than 1000 μm, the surface area of the particles decreases and, accordingly, a longer period of time is required for evaporation .

[0030] In addition, in accordance with the present invention, there is provided a permanent magnet comprising a Fe-B rare earth magnet having a predetermined configuration, and the surface of the magnet is selectively coated with evaporated metal material under the influence of a temperature difference between the temperature in the working chamber and the temperature of the magnet while the magnet reaches a predetermined temperature, when creating an atmosphere of metal vapor in the working chamber by evaporation of the evaporated metal material containing at least one of Dy and Tb, and when a magnet is introduced into the working chamber that is maintained at a lower temperature than the temperature in the working chamber, after which the magnet is subjected to heat treatment to ensure diffusion of at least one of Dy and Tb on the surface of the magnet in boundary phases of the crystal grains of a magnet.

[0031] A neodymium magnet according to the prior art is easily susceptible to corrosion, and therefore, its surface is coated with a protective film, such as resinous coatings or a nickel coating. On the contrary, the surface of the magnet according to the present invention already has a coating containing at least one of Dy and Tb, which has a very high resistance to corrosion and weathering. Thus, at least one of Dy or Tb functions as a magnet protecting film, and thus, a permanent magnet can be obtained having very high resistance to corrosion and weathering without requiring an additional protective film. Therefore, it is possible to further increase productivity and reduce manufacturing costs.

[0032] In this case, it is preferable that the surface and the boundary of the crystalline grains of the magnet have a rich phase containing at least one Dy and Tb. According to this structure, it is possible to have a permanent magnet having a very high resistance to corrosion and weathering due to the presence of a rich phase containing at least one of Dy and Tb, in addition to the presence of a rich phase on the surface of the magnet.

[0033] It is also preferred that the surface of the magnet is coated with a rich phase, and the crystal grain boundary contains 1-50% of the rich phase. If the crystal grain boundary contains a rich phase in excess of 50%, then the maximum energy product, residual magnetic induction and coercive force, which determine the magnetic properties, are significantly reduced.

Effects of the invention

[0034] The permanent magnet and the method of its manufacture in accordance with the present invention have the effect that the magnet can be manufactured with high productivity and low cost by effectively using Dy and Tb as coating materials and applying them at a high speed to the surface of the magnet type Fe-B-rare-earth elements having a predetermined configuration, and the fact that the magnet has a very high resistance to corrosion and weathering and does not require additional protective film.

[0035] Furthermore, the coating method and apparatus according to the present invention have effects in that they allow the deposition of an evaporated metal material with high yield and speed and substantially uniformly over the entire surface of a magnet having a predetermined configuration, and especially suitable for applying an evaporated metal material containing Dy and Tb to the surface of a magnet of the type Fe-B rare earth elements having a predetermined configuration.

Description of Preferred Embodiments

The best embodiment of the invention

[0036] As shown in FIGS. 1 and 2, the number 1 indicates a coating device suitable for selectively depositing evaporated metal materials, such as Dy and Tb, at high speed onto the surface of an article S, for example a sintered Fe-B rare earth magnet elements. The coating device 1 has a working chamber 2 and a preparatory chamber 3, vertically connected to each other. The working chamber 2, located above the preparatory chamber 3, is placed inside a cylindrical vacuum chamber 11, in which a predetermined vacuum level can be maintained using a vacuum means 11a, such as a turbomolecular pump, a cryogenic pump, a diffusion pump, etc.

[0037] The working chamber 2 is formed by a uniformly heated plate 21 having a cylindrical configuration open at its lower end in communication with the preparation chamber 3. The uniformly heated plate 21, with the exception of its open lower end, is surrounded by a carbon heat-insulating element 22 located inside the vacuum chamber 11. For example, a plurality of electric heaters 23, consisting of W and forming a heating means, are placed between a uniformly heated plate 21 and a heat-insulating element 22. T Thus, the space inside the working chamber 2 can be heated substantially uniformly by heating a uniformly heated plate 21 surrounded by a heat-insulating element 22, using heating means 23 in a vacuum and, accordingly, by indirectly heating the space inside the working chamber 2 by means of a uniformly heated plate 21.

[0038] As illustrated in FIG. 2, a receiver 24 having a cross section of a U-shape is placed inside the working chamber 2. The receiver 24 is used to receive an evaporated metal material on it and thus forms a placement means. The receiver 24 is fixed on the inner surface of the uniformly heated plate 21 and has an annular configuration so that the vaporized metal material transported to the working chamber 2 by means of the transport means described below can be located around the coated products S. The vaporized metal material is selected in accordance with the coating , which should be applied to the surface of the coated product, and the evaporated metal material in granular form is evenly distributed according to the reception iku 24. Receiver 24 optionally designed as a continuous ring, and may be formed as separate segments arranged at equal intervals in the circumferential direction.

[0039] A first cavity 4 is formed under the working chamber 2, and opening / closing means 5 are placed in this first cavity 4. The opening / closing means 5 includes a valve 51 and actuating means 52, such as a pneumatic cylinder, and can be moved by means of actuating means 52 between the open position (FIG. 1), in which the working chamber 2 and the preparation chamber 3 communicate with each other through the valve 51, and in a closed position in which the working chamber 2 is tightly closed by means of a valve 51 in contact with the upper plate 41 forming the first cavity 4 and sealing the hole formed in the upper plate 41. The valve 51 is provided with a second heater by means (not shown).

[0040] The second cavity 3a is located below the first cavity 4. The side wall 30 forming the second cavity 3a is provided with a shutoff valve (not shown) through which the articles to be coated S are inserted into and removed from the preparation chamber 3. The products to be coated S are held onto the support means 6. The support means 6 includes three posts 61 and two support elements 62 arranged appropriately separated from the bottom of the posts 61 and supported by the posts 61. Each post 61 has a small diameter in order to reduce heat transfer through her. This is due to the need to minimize heat transfer from the pusher element 74, described below, to the products S, i.e. sintered magnets through struts 61.

[0041] Each support element 62 is made in the form of a mesh of wires ⌀ 0.1-10 mm in order to allow covering the lower surface of articles S located on the support element 62. The distance between the support elements 62 is set depending on the height placed on products S. The support means 6 is placed inside the second cavity 3a and is mounted on a disk 63 made with a central hole 63a through which the support table, described below, can pass. The disk 63 is adapted to be placed on a support ring 64 located inside the working chamber 2.

[0042] A third cavity 3b is formed under the second cavity 3a, and these second and third cavities 3a and 3b form the preparation chamber 3. A vacuum device 31, such as a turbomolecular pump, a cryogenic pump and a diffusion pump, etc., is connected to the preparation chamber 3. Thus, the preparation chamber 3 and the working chamber 2, communicating with the preparation chamber 3 through the first cavity 4, are maintained at a predetermined vacuum level by means of a vacuum means 31. Drive means 71, such as a pneumatic cylinder, p located in the lower part of the preparation chamber 3, and the support disk 73 is mounted on the upper end of the shaft 72 of the drive means 71, which enters the preparation chamber 3. The drive means 71 and the support disk 73 form a transport means 7, and the support disk 73 can move up and down between a predetermined position (upper position) inside the working chamber 2 and a predetermined position (lower position) inside the preparatory chamber 3.

[0043] The pusher member 74, having an inverted T-shaped cross section, is mounted on the shaft 72 under the support disk 73. When the conveyance means 7 is moved to the upper position, the pusher member 74 pushes the disk 63 upward and thus presses the sealing an element (not shown), such as a metal seal located on the outer periphery of the disk 63, to the periphery of the hole made in the upper plate 41, tightly closing the working chamber 2. The pusher element 74 is provided with a third heating means (n shown).

[0044] The second cavity 3a forming the preparation chamber 3 is provided with a plasma generating means including a coil (not shown) connected to a high-frequency power source, and gas supply means 32 for supplying inert gas to the preparation chamber 3. The inert gas includes for example, a noble gas, such as He and Ar, etc. Using plasma in the preparatory chamber 3, a preliminary treatment is carried out by cleaning the surface of the article S before coating, produced in the working chamber 2, using plasma in the preparatory chamber 3. In this case, it is possible to carry out pre-treatment by cleaning the surface of the product S, using heat treatment, for example, by installing an electric heater (not shown) from W in the preparatory chamber 3, and carry out the heat treatment of the product S after coating is completed in vacuum atmosphere.

[0045] Next, the manufacture of the permanent magnet according to the present invention will be described when implementing the proposed method using the proposed device 1 with reference to FIGS. 1-3. First of all, a sintered magnet of the type Fe-B-rare-earth elements, which is a coated product, is manufactured using any known method. For example, a sintered magnet can be made by high-frequency melting a mixture of Fe, B and Nd of a predetermined composition and casting an ingot from it, then by grinding the ingot into powder and molding a magnetically ordered powder to a predetermined configuration and, finally, by sintering the molded product to obtain a sintered magnet S (see Fig. 3 (a)). Then, the sintered magnets S of a predetermined configuration are placed on the support elements 62 of the support means 6. In this case, it is preferable to place the sintered magnets S on the support elements 62 so that the direction of easy magnetization of the sintered magnets S corresponds to the direction parallel to the support elements 62.

[0046] Then, the vaporized metal material Dy is placed on the receiver 24 inside the working chamber 2. The particle diameter Dy is preferably in the range of 10-1000 μm. This is explained by the fact that, with a particle diameter of less than 10 μm, the handling of flammable Dy and Tb particles is difficult, and, on the other hand, with a particle diameter of more than 1000 μm, a longer period of time is required for evaporation. To increase the output Dy, the mass Dy placed on the receiver 24 is determined as the amount required to maintain the atmosphere of the vapor Dy in the working chamber 2 until the magnet reaches a predetermined temperature (the temperature at which the evaporated metal material diffuses not only into crystalline grain, but also to the border of crystalline grain).

[0047] The shut-off valve located on the side wall 30 is then opened to insert the support means 6 supporting the sintered magnets S into the second cavity 3a, and the support means 6 is mounted on the disk 63. Then, the shut-off valve is closed and the vacuum means 11a are actuated and 31 for pumping the vacuum chamber 11, as well as the preparatory chamber 3 and the working chamber through the first cavity 4 until then, until they reach a predetermined pressure (for example, 10 × 10 ^-6 Pa). In this case, the opening / closing means 5 is in the open position.

[0048] Then, when the pressure in the working chamber 2 and the preparation chamber 3 reaches a predetermined value, the opening / closing means 5 is moved to the closed position by the actuating means 52, so that the valve 51 closes the working chamber 2. Then, the heating means is activated 23 and a second heating means in the valve 51 of the opening / closing means 5 for heating the working chamber 2 until the temperature in the working chamber 2 reaches a predetermined value. The temperature in the working chamber is preferably set in the range of 1000-1700 ° C. This is because at a temperature below 1000 ° C it is impossible to obtain a saturated vapor pressure that can ensure the deposition of Dy on the surface of the magnet S with high speed, and, on the other hand, at temperatures above 1700 ° C, the coating period of the sintered magnet S becomes too short for uniform coverage. The temperature in the working chamber 2 is preferably in the range of 1200-1500 ° C, and more preferably in the range of 1200-1400 ° C. In these temperature ranges, the required coating thickness can be achieved at high speed.

[0049] Then, a vapor atmosphere Dy is created in the working chamber 2 having a vapor pressure of, for example, 10 Pa at 1300 ° C. Since convection occurs at a vapor pressure of 10 Pa inside the working chamber 2, a coating forms on the entire surface of the sintered magnet S, which has a normal temperature at the moment when it is introduced into the working chamber.

[0050] If the uniformly heated plate 21 forming the working chamber 2 is made of Al ₂ O ₃ widely used in conventional vacuum installations, there is a risk that Dy in the vapor atmosphere will react with Al ₂ O ₃ and form reaction products on its surface , and Al atoms will enter the atmosphere of Dy vapor. For this reason, the uniformly heated plate 21, forming the working chamber 2, the support means 6 for supporting the sintered magnets S and the support disk 73 of the conveyor 7 are made of materials that do not react with the evaporated metal materials used for coating, for example, Mo, W, V, Ta, alloys of these elements, CaO, Y ₂ O ₃ or oxides of rare earth elements. In addition, a coating of these materials can be applied to the surface of the heat-insulating element as a facing film.

[0051] While an atmosphere of Dy vapor is created in the working chamber 2, a preliminary cleaning is carried out in the preparatory chamber 3 by cleaning the surface, for example, to remove an oxide film on the surface of the sintered magnet S. In this case, it is possible to clean the surface of the sintered magnet using plasma generated in the preparation chamber 3 by supplying an inert gas, such as Ar, to the preparation chamber 3 through the gas supply means 32, and then by turning on the high-frequency power source until the pressure in The chamber 3 does not reach a predetermined value (for example, 10 × 10 ⁻¹ Pa). After completion of the pre-treatment, the temperature of the sintered material will be in the range from room temperature to 200 ° C.

[0052] When the processes of creating an atmosphere of vapor Dy in the working chamber 2 and cleaning the surface of the sintered magnet S are completed, an inert gas, such as Ar, is supplied to the preparation chamber 3 through the gas supply means 32 until the pressure in the preparation chamber 3 reaches in advance a predetermined value (for example, 1000 Pa), in order to create a pressure differential of more than two orders of magnitude relative to the pressure in the working chamber 2. When the pressure in the preparatory chamber 3 reaches a predetermined value, the working chamber 2 and the preparatory Amer 3 are connected to each other by moving the opening / closing means 5 to the open position. In this case, since the pressure in the working chamber 2 differs from the pressure in the preparation chamber 3, Ar from the preparation chamber passes into the working chamber 2, and the pressure in the working chamber 2 rises. Thus, although the vaporization has stopped (however, the heating means did not end), the entry of 2 Dy vapors formed in the working chamber into the preparation chamber is prevented.

[0053] Then, when the pressure in the working chamber 2 and the preparation chamber 3 is again reduced by means of a vacuum means 31 until it reaches a predetermined value (for example, 10 × 10 ⁻² Pa), Dy starts to evaporate again. Then, the support means 6 supporting the sintered magnets S is moved into the working chamber 2 by actuating the drive means 71 of the transport means 7. In this case, the working chamber 2 is tightly closed by a sealing element, such as a metal seal, located on the periphery of the disk 63, which is in close contact with a surface around the hole formed in the upper plate 41.

[0054] Then, when the heated working chamber 2 is tightly closed again, for example, an atmosphere of saturated vapor Dy with a pressure of 10 Pa at a temperature of 1300 ° C is created in the working chamber 2, and this state is maintained for a predetermined period of time. In this case, since sintered magnets having a lower temperature than the temperature in the working chamber 2 were introduced into the working chamber 2, pairs Dy are selectively deposited on the surface of the sintered magnets S due to the temperature difference between the temperature in the working chamber 2 and the temperature S magnets (coating step). Thus, Dy can be deposited at high speed only on the surface of the sintered magnets S (FIG. 3 (b)). In this case, Dy is not deposited on the pusher element 74 of the support table 73, since the pusher element 74 is heated to substantially the same temperature as the temperature of the uniformly heated plate 21 using a third heating means (not shown).

[0055] Since not only Dy, but also the sintered magnets S themselves are heated by the radiated heat, when the sintered magnets S, having a normal temperature, are introduced into the working chamber 2 heated to a high temperature, the exposure time in the working chamber 2, in which the atmosphere is created saturated vapor, corresponds to the period for which the sintered magnets S reach a temperature of 900 ° C, as well as the period for which the necessary amount of Dy is deposited on the surface of the sintered magnets S (in this case, “the required amount of Dy) means the amount in which Dy diffuses uet only crystal grain boundary to improve sintered S) of the magnetic properties of the magnets. If the sintered magnets S are heated to a temperature above 900 ° C, Dy will diffuse into the grains (crystalline grains of the main phase) of the magnets S. Ultimately, this situation will be similar to the addition of Dy during the manufacturing of a permanent magnet and, therefore, there is a risk that tension magnetic field, and therefore, the maximum energy product, which determine the magnetic properties, will be significantly reduced.

[0056] Incidentally, when the sintered magnet S thermally expands due to heat, the thermal expansion of the sintered magnet S reveals an anomaly similar to an invar alloy anomaly at temperatures below the Curie temperature (approximately 300 ° C) and, thus, peeling of the coating deposited can occur. on the surface of the magnet S. Therefore, the exposure time is preferably such that the maximum temperature of the sintered magnet S is below 250 ° C or above 450 ° C. This is explained by the fact that at temperatures below 250 ° C, peeling of the coating deposited on the surface of the magnet is difficult because the stress due to the thermal expansion anomaly decreases, and, on the other hand, adhesion between the magnet and Dy deposited on the surface above 450 ° C on the surface of the magnet is improved by melting a portion of the magnet, and thus peeling of the coating deposited on the surface of the magnet is difficult.

[0057] On the other hand, an inert gas, such as Ar, is supplied to the preparation chamber 3 through the gas supply means 32 until the pressure in the preparation chamber 3 reaches a predetermined value (for example, 1000 Pa). After a predetermined period of time has elapsed after the sintered magnets S are transported to the working chamber 2, the support disk 73 moves from the upper position in the working chamber 2 to the lower position in the preparation chamber 3, and the opening / closing means 5 moves from the open position to the closed position. In this case, the pairs Dy are not deposited on the valve 51 of the opening / closing means 5, since the valve 51 is heated by a second heating means (not shown) to a temperature substantially the same as the temperature of the uniformly heated plate 21. The vaporization is stopped due to that Ar from the preparation chamber 3 penetrates into the working chamber 2, and the sintered magnets S, which are coated with Dy, are cooled in an Ar atmosphere.

[0058] Then, in the preparatory chamber 3, isolated from the working chamber 2, a vacuum is created using a vacuum means 31 until the pressure in the preparatory chamber 3 reaches a predetermined value (10 × 10 ^-3 Pa), and heat treatment is carried out sintered magnets S coated with Dy for a predetermined time at a predetermined temperature (for example, 700-950 ° C) by actuating heating means located in the preparation chamber 3 (diffusion step). In this case, it is preferable, continuously with heat treatment in the preparatory chamber 3, to conduct heat treatment to relieve stress from the permanent magnets for a predetermined time (e.g., 30 minutes) at a predetermined temperature (e.g., 500-600 ° C), lower compared with the temperature of the above heat treatment (annealing step). Ultimately, the support means 6 is removed from the preparatory chamber 3 by opening the shutoff valve on the side wall 30 after cooling for a predetermined period of time.

[0059] Thus, it is possible to obtain permanent magnets on which Dy covers the entire surface of the sintered magnets S and conduct heat treatment to uniformly diffuse Dy deposited on the surface of the magnets S into the boundary phases of the crystal grains of the magnets (Fig. 3 (c)) . The neodymium magnet of the prior art is easily susceptible to corrosion, and therefore, its surface is coated with a protective coating of resin, such as epoxy resin or PPS (polyphenylene sulfide), or surface treatment such as nickel plating is carried out. The surface of the magnet in accordance with the present invention has a coating of Dy having a very high resistance to corrosion and weathering compared to Nd, and thus, a permanent magnet having a very high resistance to corrosion and weathering can be obtained, requiring no additional protective films. Therefore, due to the absence of additional surface treatment steps, it is possible to coat Dy on the surface of the magnets at a high speed and at a predetermined coating thickness, as well as further increase productivity and reduce manufacturing costs.

[0060] Preferably, the surface and the grain boundary of the magnet magnet have a Dy-rich phase (phase containing 5-80% Dy). The prior art neodymium magnet has three phases, including a main phase, an Nd-rich phase, and a B-phase rich. Since, in accordance with the present invention, a rich Dy phase is present in the Nd-rich phase at the crystalline grain boundary, which has low resistance to corrosion and weathering, permanent magnets having very high corrosion resistance and weathering resistance can be produced, and at the same time in that a rich Dy phase is present on the surface of the sintered magnets S.

[0061] More preferably, the surface of the sintered magnets S is coated with a Dy-rich phase, and the crystal grain boundary includes a Dy-rich phase in an amount of 1-50%. On the other hand, when the crystalline grain boundary includes a Dy-rich phase with a content of more than 50%, the maximum energy product, residual magnetic induction and coercive force, which determine the magnetic properties, are significantly reduced.

[0062] Although the present invention has been described with respect to conducting Dy coating on the surface of sintered S magnets of type Fe-B rare earth elements, the coating method and apparatus 1 of the present invention is not limited to such an embodiment and can be used for coating from other evaporated metal materials. In this case, conditions, such as the heating temperature in the working chamber 2 and the exposure time, etc., are set in accordance with the products to be coated and the properties of the evaporated metal materials. In addition, Tb can be used in place of Dy and, at a high speed and selectively, coat Tb from the sintered magnets of the Fe-B rare earth type using the coating method and apparatus of the present invention. In addition, it is possible to carry out the diffusion step in the working chamber 2 after the coating has been completed.

[0063] Furthermore, an alloy containing at least one of Dy and Tb and at least one of Nd, Pr, Al, Cu, Ga and Ta can be used as an evaporated metallic coating material to increase the coercive force. Such an alloy can additionally increase, first of all, the coercive force in comparison with the permanent magnets obtained by heat treatment. In this case, since Dy and Tb have a high melting point, it is preferable to use materials having a lower melting point compared to them to create an evaporated metal material in a shorter time.

[0064] Although in the illustrated embodiment, the preparatory chamber 3 is located under the working chamber 2, it is possible to place the working chamber 2 under the preparatory chamber 3. As shown in Fig. 4, in comparative measurements of the density Ar, He and Dy at constant pressure and temperature, the density Dy and Ar at constant pressure is comparable, for example, the density of Ar at a pressure of 10 Pa and at room temperature (about 27 ° C) and the density of Dy at a pressure of 10 Pa and high temperature (about 1300 ° C). Based on this fact, it is possible to reliably prevent the leakage of vapors Dy from the working chamber 2 into the preparation chamber 3 due to the difference in specific gravity when the sintered magnets S are removed from the working chamber 2 by supplying He gas, which has a large difference in density with respect to constant pressure in the preparation chamber 3, so that the pressure in the working chamber 2 and the pressure in the preparation chamber 3 are substantially the same when the working chamber 2 is under the preparation chamber 3.

[0065] Although in the illustrated embodiment, the design is such that heat transfer to the sintered magnets S through struts 61 is difficult, the present invention is not limited to such a design and any cooling means can be provided to force the temperature rise of the sintered magnets S. In this case, cooling can be provided. means for containing the temperature increase of the sintered magnets S heated by the radiated heat when the magnets S with ordinary temperature are introduced into the working chamber 3, on heated to a high temperature by circulating refrigerant (cooling water) through racks 61 with an increase in the diameter of each rack.

Option exercise No. 1

[0066] Each sintered magnet of the type Fe-B-rare-earth elements was made in the form of a rectangular parallelepiped with dimensions of 50 × 50 × 8 mm, using a starting material having the composition 31Nd-1Co-1B-0,1Cu-ost Fe ("NEOMAX -50 ”manufactured by NEOMAX Co.). The surface of the sintered magnet S was cleaned with acetone after its finishing to obtain a surface roughness of less than 20 μm.

[0067] Dy was applied to the surface of the sintered magnet S using the apparatus 1 and the coating method in accordance with the present invention. As the coating material, Dy was used with a purity of 99.9% and a mass of 500 g, which was placed on the receiver 24. The wire forming the mesh support element 62 of the support means 6 is made of Mo and has a diameter of 1 mm. Then four (4) peeled sintered magnets S were placed on each support element 62 in a circle with a diameter of 80 mm in the diametrical direction against each other (a total of eight (8) sintered magnets S were placed on two support elements 62 of the upper and lower tiers). The distance between the supporting elements 62 of the upper and lower tiers is 60 mm.

[0068] Before coating from Dy, Ar was supplied to the preparation chamber 3, and the surface of the sintered magnet S was cleaned for 60 seconds by plasma treatment at a pressure of 10 × 10 ⁻¹ Pa and a high-frequency voltage of 800 V. The temperature of the sintered magnet S after cleaning was equal to 60 ° C.

[0069] On the other hand, the working chamber 2 was closed using the opening / closing means 5 in its closed position, and heated to a temperature of 1350 ° C to vaporize Dy and fill the working chamber 2 with Dy vapor. The pressure in the working chamber 2 and the preparatory chamber 3 when placing the sintered magnets S in the atmosphere of the vapor Dy was set to 10 × 10 ^-2 Pa, and the exposure time after putting the sintered magnets S in the working chamber 2 was set to 40 seconds. In addition, heat treatment conditions in the preparatory chamber 3 were such that the pressure in the preparatory chamber 3 was set at 10 × 10 ^-3 Pa, and the holding time of 5 minutes was set at 800 ° C and 30 minutes at a temperature of 600 ° C .

[0070] FIG. 5 is a table showing average magnetic properties of eight (8) permanent magnets manufactured under the above conditions. The magnetic properties of magnets without a coating of Dy are also shown in the table of FIG. 5 as comparative examples. Based on these results, it was found that permanent magnets having high magnetic properties were obtained, such as a maximum energy product of 50.3 MGE, residual magnetic induction of 14.4 kG and a coercive force of 23.5 kOe. The temperature of the sintered magnet S after exposure for 40 seconds was approximately 600 ° C, and the coating thickness was approximately 100 μm, with the coating being formed on the surface of the sintered magnet S substantially uniformly.

Option exercise No. 2

[0071] In Embodiment No. 2, permanent magnets were manufactured under the same conditions as in Embodiment No. 1, except that no heat treatment was performed. However, the exposure time of the permanent magnets in the atmosphere of the vapor Dy was set equal to one (1) minute, and the temperature in the working chamber changed. 6 is a table showing average values of the thickness of the coating of Dy when the coating was applied under these conditions, and the magnetic properties of the permanent magnets manufactured in this embodiment. In accordance with embodiment No. 2, it can be found that at a temperature below 1000 ° C, a coating is practically not formed, however, at a temperature above 1200 ° C, the coating can form at a high speed of more than 20 μm / s. In this case, it was found that it is possible to obtain a permanent magnet having a maximum energy product of about 50 MGE with low losses and a high coercive force of 17 kOe or more in the temperature range of 1100-1700 ° C.

Option exercise No. 3

[0072] In Embodiment No. 3, permanent magnets were manufactured under the same conditions as in Embodiment No. 1, except that no pre-treatment (cleaning) was performed. However, the exposure time of permanent magnets in the atmosphere of Dy vapor varied. 7 is a table showing average values of the coating thickness of Dy obtained by changing the exposure time, maximum energy product and magnetic properties of the permanent magnets made in accordance with this embodiment. According to Embodiment No. 3, it can be found that a vapor deposition rate of more than 17 μm can be provided, and that the temperature of the sintered magnet itself is at most 743 ° C., although it is held for 60 seconds. In this case, it was found that it is possible to obtain a permanent magnet of high coercive force having a maximum energy product of about 50 MGse, a residual magnetic induction of 14.5 kG and a coercive force of 15.4-21.3 kOe.

Option exercise No. 4

[0073] In Embodiment No. 4, permanent magnets were manufactured under the same conditions as in Embodiment No. 1, except that no pre-treatment (cleaning) was performed. However, the wire for forming the mesh support element 62 of the support means 6 was made of Mo and had a diameter of 3 mm. Fig. 8 is a table showing magnetic properties when such a wire of 3 mm diameter is used in the manufacture of the support member 62. In accordance with embodiment No. 4, it can be found that, in spite of the remaining uncoated sections in the form of a mesh on the surface of the sintered magnet S adjacent to the supporting element 62 made of thick wire, this practically does not affect the coating of the magnet S during the coating operation on mesh support element 62, when the magnet S is located on the support element 62, taking into account the direction of easy magnetization, and thus, it is possible to obtain a magnet of high coercive force having a maximum energy product of 50.0 MGSE, residual magnetic induction of 14.4 kG and coercive force of 21.3 kOe.

Option exercise No. 5

[0074] In Embodiment No. 5, permanent magnets were manufactured under the same conditions as in Embodiment No. 1, however, the exposure time of the sintered magnet in the atmosphere of the Dy vapor varied. Fig. 9 (a) is a table showing average values of the coating thickness of Dy at the measured points shown in Fig. 9 (b) (measured points (1) to (15)). According to this table, in FIG. 9 (a), it has been found that a substantially uniform coating can be obtained.

Option exercise No. 6

[0075] In embodiment No. 6, each sintered Fe-B rare-earth magnet was made in the form of a rectangular parallelepiped with dimensions of 3 × 50 × 40 mm using a starting material having the composition 22Nd-5Dy-0.9B-4Co-ost .Fe. In this case, the surface of the sintered magnet S was finished to a surface roughness of less than 50 μm.

[0076] Then, a metal coating was formed on the surface of the sintered magnet S using the device 1 and the coating method in accordance with the present invention. A starting material having a composition of 10Dy-5Tb-50Nd-35Pr was used as a coating material and placed on the receiver 24. The wire forming the mesh support element 62 of the support means 6 was made of Mo and had a diameter of 1 mm. One hundred (100) sintered magnets S, cleaned as described above, were arranged so that they were diametrically opposed to each other on the support element 62.

[0077] On the other hand, the working chamber 2 was tightly closed when the opening / closing means 5 was closed and heated to 1250 ° C to evaporate the vaporized coating material having the above composition, creating an atmosphere of metal vapor in the working chamber 2. Pressure in the working chamber 2 and the preparatory chamber 3 by placing the sintered magnets S in an atmosphere of metal vapor was set to 10 × 10 ^-2 Pa, and the pressure in the preparatory chamber 3 was set substantially the same as the pressure in the working chamber 2 by the hearth and He gas in the preparatory chamber 3.

[0078] The holding time after the sintered magnets S were transported to the working chamber 2 was set to 10-300 seconds, so that the maximum temperature of each sintered magnet became 100-1000 ° C. In this case, each rack 61 was cooled by water. In addition, the heat treatment conditions in the preparation chamber 3 were such that the pressure in the preparation chamber 3 was set to 10 × 10 ⁻³ Pa, and the exposure time was one (1) hour at a temperature of 800 ° C (diffusion step) and 30 minutes at a temperature of 600 ° C (annealing step). Then the pressure in the preparatory chamber 3 was brought back to atmospheric pressure, and the magnets were removed from it.

[0079] FIG. 10 is a table showing the magnetic properties of a hundred (100) permanent magnets manufactured under the above conditions and the proportion of defective products with poor adhesion detected during peeling tests using adhesive tape. In accordance with these results, it was found that when the maximum temperature of the sintered magnets S does not reach 100 ° C, the coating material does not deposit on the surface of the sintered magnets S and thus a high coercive force cannot be obtained. On the other hand, it has been found that when the maximum temperature is in the range of 100-1050 ° C., a coating material of a thickness of 10 μm or more is deposited on the surface of the sintered magnet S, and a permanent magnet of high coercive force having a maximum energy product of 44 MCE can be obtained or more, a residual magnetic induction of 13.8 kG or more and a coercive force of 28 kOe or more. However, it was also found that when the temperature of the sintered magnet S is in the range of 250-450 ° C, the proportion of defective products with poor adhesion is less than 10%. In embodiment No. 6, since prior to the coating of Dy, the surface of the sintered magnets was not preliminarily cleaned, the penetration of Dy into the grains of the sintered magnet was blocked during the coating operation and, thus, it was found that the maximum energy product determining the magnetic properties did not decrease , despite the fact that the maximum temperature of the sintered magnets exceeded 900 ° C.

Option exercise No. 7

[0080] In Embodiment No. 7, each sintered Fe-B rare-earth magnet was made in the form of a rectangular parallelepiped with dimensions of 5 × 50 × 40 mm using a starting material having the composition 28Nd-1B-0.05Cu-0.17Zr -ost.Fe. In this case, the surface of the sintered magnet S was finished, after which the surface roughness was less than 50 μm, and then was cleaned with acetone.

[0081] Then, Dy was coated on the surface of the sintered magnet S using the apparatus 1 and the coating method in accordance with the present invention. In this case, Dy with a purity of 99.9% was used as the coating material and placed on the receiver 24. One hundred (100) sintered magnets S, cleaned as described above, were placed in such a way that they were diametrically opposed to each other on the support member 62.

[0082] Before the coating operation, Ar was fed into the preparation chamber 3 and the surface of the sintered magnet was treated with plasma for 60 seconds under conditions of a pressure of 10 × 10 ⁻¹ Pa and a high-frequency voltage of 800 V. The temperature of the sintered magnet S after this cleaning was 60 ° C.

[0083] On the other hand, the working chamber 2 was closed by means of the opening / closing means 5 in the closed position and heated to 1200 ° C to evaporate Dy and create an atmosphere of metal vapor in the working chamber 2. The pressure in the working chamber 2 and the preparation chamber 3 when placing the sintered magnets S in the atmosphere of the vapor Dy was set to 10 × 10 ^-2 Pa, and the exposure time was set so that after it was possible to obtain a coating thickness of 20 μm on average after the sintered magnets S were introduced into the working chamber 2. Cr IU of heat treatment conditions in the preparatory chamber 3 were such that the pressure in the preparatory chamber 3 equal to 10 × 10 ^-3 Pa was installed and the holding time was set to one (1) hour at a temperature of 950 ° C (step diffusion) and 30 minutes at a temperature of 500 ° C (annealing step). Then the pressure in the preparatory chamber 3 was brought back to atmospheric pressure, and the magnets were removed from it.

Comparative examples

[0084] Sintered magnets S were manufactured under the same conditions as in embodiment No. 7, as comparative examples 1-3. In comparative example 1, permanent magnets were obtained by coating an epoxy resin with an average thickness of 20 μm on the surface of a hundred (100) sintered magnets S, using a known method instead of forming a coating of Dy and performing heat treatment of the surface of the magnets S. In comparative example 2, on the surface One hundred (100) sintered S magnets applied a nickel coating with an average thickness of 20 μm using the known nickel plating method. In comparative example 3, an aluminum coating with an average thickness of 20 μm was deposited onto the surface of a hundred (100) sintered magnets S using a known vapor deposition method.

[0085] Fig. 11 is a table showing the results of comparing permanent magnets obtained in accordance with Embodiment 7 and Comparative Examples 1-3 and respectively sintered magnets S (Comparative Example 4) in terms of magnetic properties, corrosion resistance and weather resistance. . The following tests were carried out for resistance to corrosion and weathering: tests with visual inspection confirming the formation or absence of corrosion after 100 hours after spraying salt water on the surface of permanent magnets and sintered magnets; tests at saturated water vapor pressure (pressure cooking) for 100 hours; and tests with visual inspection confirming the formation or absence of corrosion after holding for 1000 hours at 80 ° C and 90% humidity.

[0086] In accordance with the comparison, it was found that the permanent magnet in accordance with embodiment No. 7 of the present invention has high magnetic properties: the maximum energy product of 56 MGse, the residual magnetic induction of 15.0 kG and the coercive force of 28 kOe compared to the coercive force 10 kOe in comparative examples 1-4. In addition, it was also found that in comparative examples 1-4, when corrosion tests or weathering tests, the fact of corrosion was confirmed, while during such tests in the embodiment No. 7 of the present invention was not detected corrosion and, therefore, permanent magnets made in accordance with the present invention, have high corrosion resistance and resistance to weathering.

Option exercise No. 8

[0087] In embodiment No. 8, each sintered Fe-B rare-earth magnet was made in the form of a rectangular parallelepiped with dimensions of 50 × 50 × 8 mm, using a starting material having the composition 31Nd-1Co-1B-0,1Cu-ost .Fe ("NEOMAX-50" manufactured by NEOMAX Co.). The surface of the sintered magnet S was cleaned with acetone after finishing to obtain a surface roughness of less than 20 μm.

[0088] An evaporated metal material was deposited on the surface of the sintered magnet S using the device 1 and the coating method in accordance with the present invention. An alloy containing Dy and Nd, Pr, Al, Cu, Ga, Ta mixed with Dy in accordance with a 1: 1 stoichiometric ratio was used as the evaporated metal material and placed on the receiver 24. Before applying the evaporated metal material to the preparation chamber 3, Ar was fed and the surface of the sintered S magnet was treated with plasma for 60 seconds under conditions of a pressure of 10 × 10 ⁻¹ Pa and a high-frequency voltage of 800 V. The temperature of the sintered magnet S after cleaning was 60 ° C.

[0089] On the other hand, the working chamber 2 was closed by means of the opening / closing means 5 in the closed position and heated to 1350 ° C to evaporate the vaporized metal material and fill the working chamber 2 with metal vapors. The pressure in the working chamber 2 and the preparatory chamber 3 when placing the sintered magnets S in the atmosphere of metal vapors was set to 10 × 10 ^-2 Pa, and the exposure time was set so that after placing the sintered magnets S in the working chamber 2, a coating with a thickness of approximately 30 microns. In addition, the heat treatment conditions in the preparation chamber 3 were such that the pressure in the preparation chamber 3 was set equal to 10 × 10 ^-3 Pa, and the exposure time was set to 5 minutes at a temperature of 800 ° C (diffusion step) and 30 minutes at temperature 600 ° С (annealing step).

[0090] FIG. 12 is a table showing the magnetic properties of permanent magnets manufactured under the above conditions. This table also shows the magnetic properties of magnets in which only Dy was used as the evaporated metal material, and magnets in which an alloy containing Dy and Ni, Co, Fe, Au, Pt, Ag mixed with Dy according to stoichiometric ratio

1: 1. Based on these results, it was found that the permanent magnets from the comparative examples have significantly lower magnetic properties, especially the coercive force and maximum energy product, compared with permanent magnets containing only Dy coating. On the other hand, it has been found that the permanent magnets according to Embodiment No. 8 of the present invention have high magnetic properties, especially coercive force, in comparison with magnets containing only Dy coating, and that permanent magnets having high magnetic properties can be obtained: the maximum energy product ((HV) max) of 50.0 MGse or more, the residual magnetic induction (Br) of 14.0 kG or more and the coercive force (Hcj) of 24.1 kOe or more.

Brief Description of the Drawings

[0091] FIG. 1 is an explanatory schematic drawing showing a structure of a coating device of the present invention.

FIG. 2 is an explanatory drawing showing support means for supporting sintered magnets, i.e. covered products in the working chamber.

Figure 3 is an explanatory drawing showing the steps of manufacturing a permanent magnet of the present invention.

4 is a graph showing the relationship between temperature and density of Ar, He, and Dy.

5 is a table showing average values of magnetic properties of permanent magnets made in Embodiment No. 1.

6 is a table showing average values of the thickness of the coating applied in embodiment No. 2, and the magnetic properties of the permanent magnets made in embodiment No. 2.

7 is a table showing average values of the coating thickness and the maximum temperature of the coating of Dy in embodiment No. 3 and the magnetic properties of the permanent magnets made in embodiment No. 3.

Fig. 8 is a table showing average values of magnetic properties of a permanent magnet manufactured in Embodiment No. 4.

Fig.9 is a table showing the average values of the thickness of the coating on the surface of the magnet coated in the embodiment No. 5.

Figure 10 is a table showing the magnetic properties and the percentage of defective products with low adhesion of the permanent magnet coating obtained in embodiment No. 6.

11 is a table showing magnetic properties, corrosion resistance, and weather resistance in accordance with embodiment No. 7 and in comparative examples 1-4.

12 is a table showing the magnetic properties of a permanent magnet manufactured in Embodiment No. 8.

[0092] 1 is a coating device

2 - working chamber

3 - preparatory chamber

5 - means of opening / closing

6 - supporting means

7 - vehicle

S - coated products (sintered magnets)

Claims (21)

1. The coating method, comprising a first step, including heating the working chamber and creating an atmosphere of metal vapor inside the working chamber by evaporating the vaporized metal material previously placed inside the working chamber, and a second step comprising introducing into the working chamber of coated products, supported at a lower temperature than the temperature in the working chamber, and subsequent selective deposition of the evaporated metal material on the surface of the coated product under the influence of differences s the temperature between the temperature in the working chamber and the temperature of the coated products. 2. The coating method according to claim 1, in which in the working chamber create an atmosphere of metal vapor in a saturated state. 3. A coating device comprising a working chamber, a preparatory chamber in communication with the working chamber, a vacuum means for maintaining the working and preparatory chambers at a predetermined vacuum level, an opening / closing means moving between an open position in which the working and preparatory chambers communicate with another, and in a closed position in which the working chamber is tightly closed, a transport means for moving the coated products between the working chamber and the preparatory chamber Black and tightly closing the working chamber, when the products to be coated are moved into the working chamber when the opening / closing means is open, a receiver for accommodating the evaporated metal material placed on it in the working chamber, and heating means for substantially uniformly heating the interior of the working chamber to high temperature in the closed position of the opening / closing means, while the coated products in the preparation chamber are moved into the working chamber by means of a transport means when the opening / closing means is moved to an open position for selectively depositing the vaporized metal material on the surface of the coated article under the influence of a temperature difference between the temperature in the working chamber and the temperature of the coated articles. 4. The device according to claim 3, additionally containing a vacuum chamber, inside which there is a working chamber, and which is equipped with another vacuum means, and a heat-insulating element, while the working chamber is formed by a uniformly heated plate made with an opening in one of its lateral sides, heat-insulating the element is positioned so that it encloses a uniformly heating plate, with the exception of the specified side with the specified hole, and the heating means for heating is ERNO heater plate is disposed between the heater plate and uniformly heat insulating member. 5. The device according to any one of claims 3 or 4, further comprising a gas supply means for supplying an inert gas to the preparation chamber so as to maintain a negative pressure in the working chamber relative to the pressure in the preparation chamber. 6. The device according to any one of claims 3 or 4, wherein the preparation chamber is equipped with gas supply means for supplying gaseous helium to the preparation chamber in such a way as to maintain the pressure in the working chamber substantially the same as the pressure in the preparation chamber. 7. The device according to claim 6, in which the working chamber is located under the preparatory chamber. 8. The device according to any one of claims 3 or 4, in which the receiver for receiving the evaporated metal material on it is made in the form of a ring so that the evaporated metal material can be located around the coated products when these coated products are moved into the working chamber with transportation means. 9. The device according to any one of claims 3 or 4, in which the preparatory chamber is equipped with a plasma generating means for cleaning the surface of the coated product using plasma. 10. The device according to any one of paragraphs.3 or 4, in which the preparatory chamber is equipped with other heating means for cleaning the surface of the coated product by heat treatment with the supply of inert gas to the vacuum atmosphere or the preparatory chamber through the associated gas supply means. 11. The device according to any one of claims 3 or 4, in which the evaporated metal material is Dy or Tb or an alloy containing at least one of Dy and Tb, and the coated product is a sintered magnet of the type Fe-B rare earth elements having in advance predefined configuration. 12. A method of manufacturing a permanent magnet of the type Fe-B-rare-earth elements having a predetermined configuration, comprising applying an evaporated metal material containing at least one of Dy and Tb to the surface of a pre-sintered magnet and diffusing the vaporized metal material deposited on the surface of the sintered magnet, along the boundaries of the crystalline grains of the sintered magnet by heat treatment at a predetermined temperature, while the coating includes the first stage of heating the working chamber used to carry out the coating step and creating an atmosphere of metal vapor inside the working chamber by evaporating the evaporated metal material previously placed inside the working chamber, and the second stage of introducing a sintered magnet into the working chamber, which was maintained at a lower temperature than temperature in the working chamber, and subsequent selective deposition of the evaporated metal material on the surface of the magnet under the influence of the temperature difference between the temperature the temperature in the working chamber and the temperature of the magnet until the magnet reaches a predetermined temperature. 13. A method of manufacturing a permanent magnet according to item 12, in which in the working chamber create an atmosphere of metal vapor in a saturated state. 14. A method of manufacturing a permanent magnet according to any one of paragraphs.12 or 13, in which the evaporated metal material further comprises at least one of Nd, Pr, Al, Cu, Ga and Ta. 15. A method of manufacturing a permanent magnet according to any one of paragraphs.12 or 13, in which the temperature of the magnet in the second stage is less than 250 ° C or more than 450 ° C. 16. A method of manufacturing a permanent magnet according to any one of paragraphs.12 or 13, further comprising the step of cleaning the surface of the magnet in a vacuum atmosphere before introducing it into the working chamber. 17. A method of manufacturing a permanent magnet according to any one of paragraphs.12 or 13, in which the temperature in the working chamber at the first stage is set in the range of 1000-1700 ° C. 18. A method of manufacturing a permanent magnet according to any one of paragraphs.12 or 13, in which the particle diameter of the evaporated metal material located inside the working chamber at the stage of coating is in the range of 10-1000 microns. 19. A permanent magnet made of a sintered magnet of the type Fe-B-rare-earth elements having a predetermined configuration, the surface of which is selectively coated with evaporated metal material under the influence of the temperature difference between the temperature in the working chamber and the temperature of the magnet until the magnet reaches a predetermined temperature, creating an atmosphere of metal vapor in the working chamber by evaporation of the evaporated metal material containing at least one of Dy and Tb, and when magnesium is introduced into the working chamber one was maintained at a lower temperature than the temperature in the processing chamber, whereupon the magnet is heat treated in order to ensure the diffusion of at least one of Dy and Tb on crystal grain boundaries of the magnet. 20. The permanent magnet according to claim 19, in which the surface and the boundaries of the crystal grains of the magnet contain a phase rich in the content of at least one of Dy and Tb. 21. The permanent magnet according to any one of claims 19 or 20, wherein the magnet coating is a phase rich in at least one of Dy and Tb, and 1-50% of said phase is contained at the grain boundaries.

Images